Microphone arrangement



Patented 'Alpi'. .516-, 194.0

PATENT OFFICE p 2,197,691 y MICROPHONE ARRANGEMENT Erwin Gerlach, Berlin, Germany, assignor to Tele-I funken Gesellschaft fr Drahtlose Tclegraphie m. b. H., Berlin, Germany, a corporation of Germany Application February z, 193s, serial No. 188,249

In Germany February 19, 1937 s claims. (ci. 179-91) The invention relates to improved microphone apparatus and particularly to microphones for electro-acoustic transmissions wherein there.

the use of a cable having a multiplicity o f wires for connecting the line between the microphone and the main control station. The length of such a cable is often several hundred meters, the operating voltages required by a microphone having an amplifier stage mounted thereon can be applied to the microphone across the cable, but if cables having only two wires are to be used for the transmission, a preliminary ampliiier is required in the direct proximity of the microphone. This preliminary amplifier supplies the microphone with the proper voltages. microphone with tube, for example, requires a tube heater voltage, plate voltage and grid voltage.

It has been found undesirable to mount the preliminary amplifier directly on the microphone. Therefore, it will be more appropriate to place the preliminary amplifier at a distance of about ten to twenty meters from the microphone because in this arrangement the said ampliiier canK ings, opera transmissions, transmissions of speeches, etc.

In accordance with this invention, the microphone with its amplifier stage mounted thereon'A so that when winding or unwinding the cable,A

the amplier will likewise be turned. This afiords the advantage that the end of the cable for the preliminary amplilier remains xedly connected with' the amplifier.I Thus, during the operation,'the winding or unwindingcan be carried out without the necessity of connecting vto slip rings and the like, which vlines have direct voltage and are very sensitive todisturbances at the places of contact. Even when during operation or testing there" is no reason to. vary the length of the line, it would not be proper to use slip rings as they cause the possibility of cracky ling noises.

A condenser- In accordance with a further feature of this invention, when slip rings are employed to permit spool 3 to rotate independently of spool 2, they are placed in the low impedance circuit 0I the actual distance line containing two wires. The danger of slip ring-noisesvis in this case extremely small. Obviously, it is also possible to connect the double wire distance line to ilxed. terminals instead of slip rings.v At the winding and unwinding, this connection must then be opened.

In many cases, it may be desirable to mount `a cable drum on the apparatus'having double wire distance cable connected thereto so that there will always be connected a part of the double wire cable directly with the preliminary amplier so'that in cases where the place at which the preliminary amplifier iis to be'set up isalso suitable for setting up other amplifiers, the lconnection with the 'ampliiier can alwaysbe im-v mediately established.

The protective casing for the apparatus surrounds both cable drums, the slip rings and the preliminary amplifier. The cables emerge through two openings. An especially provided space (not shown) within the protective casing serves for accommodating the microphone so that when the latter is packed up it n eed not be separated from the cable. f

The figure shows an example embodying the idea of the invention. A casing' or a drum i preferably formed of sheet metal has two cable spools 2 and 3 vrotatably mounted therein. 'I'he cable spool 2 serves for winding on the cable 5 leading to the microphone 4. An operating` crank I5 is fastened to yshaft Vlli for rotation -of spools 2 and are passed to the main amplier or frequency` input source. in order to eliminate improper contacts to which preliminary amplifiers are -extremely sensitive, the preliminary amplier 'l indicated by the dash lines inside the cable spool 2 is iix'edly mounted within said spool 2, so that it will turn when the cable for the microphonel is being wound on. The terminals to which the microphone cable is connected are designated by 8, and the terminals from which the connections lead to the main amplifier, namely the output terminals of the ampliiier l, are designated by 9.

As can be seen from the arrangement shown, the microphone cable is xedly connected to the microphone, as well as to the preliminary ampliiler, so that difllculties due to improper contacts such as are encountered when using slip rings -in the portion of the cable, win not be possible. In order that the impulses furnishedby the aml plier l can be applied to the main amplifier,

in. In this case, the opening l@ must be large enough to permit insertion of the microphone d. This opening will then preferably be closed up by means of a sliding cover. In this way, a sin-n gle unit that can be easily carried is obtained and whichfulfills all requirements as regards simple handling land compactness. Thisl is of importance in case of microphones used for reporting, for talking nlm recording, transmission of speeches, etc.

If a still simpler construction is desired, the

'A possibility exists of accommodating only the cable spool 2 including the preliminary amplier l within the cable drum. Such construction may be considered, for instance, where the cable drum is to be placed in direct vicinity of the central amplifier station.

What is claimed is:

1. A microphone arrangement comprising a casing, a cable and spool located within said casing, said spool having a hollow portion ad- -jacent the winding space for said cable, and an amplifier, which is electrically connected to said microphone by said cable, disposed within said hollow 'portionl 2. A microphone arrangement having a wound-on line cable comprising a casing for enclosing a spool for said cable, an amplifier mounted to rotate within said spool, and means including said cable electrically connecting said microphone and amplifier directly together.

3. A microphone arrangement comprising a casing for enclosing a. microphone, a microphone cable divided into a plurality of portions, and a rotatable spool for each divided portion of said cable, an amplifier mounted to rotate within one of said spools, and means including one portion of said cable electrically connecting said microphone and amplifier directly together. '4. A microphone arrangement comprising'` aarancel casing for enclosing a microphone, a microphone cable dividedinto a. plurality of portions, and a rotatable spool for each divided portion of said `cable an amplifier mounted adjacent one of said spools, and means including that portion of the cable which is wound upon the spool adjacent said amplifier forming a direct-connection between said microphone and said amplifier.

5. A microphone arrangement comprising a casing for enclosing a microphone, a microphone cable divided into two portions, two separate winding spoolsfor saidcable portions. an amplifier arranged to rotate with one of said spools,

one portion of said cable being wound on one of said spools and connected directly to said microphone and said amplifier, the other portion of said cable being wound upon the other spool and serving as a connection from said amplifier to a utilization point.

6. A microphone arrangement comprising a casing for enclosing a microphone, a. microphone cable divided into two portions, two separate winding spools for said cable, an amplifier arranged to rotate with one of said spools, one portion of said cable being woundl on one o f said spools and connected directly to said microphone and said amplifier, the other portion of said cable being wound upon said other spool, said last-mentioned spool having slip rings located thereon, and means for connecting said amplifier through said slip rings to said other portion of said cable.

7. A microphone arrangement comprising a casing for enclosingv a microphone, a microphone cable divided into two portions, two separate 'winding spools for said cable, one of said spools having a. large central aperture, an amplifier 1ocated within said central aperture and arranged to rotate with said one spool, one portionI of said 'cable being wound on said spool having the large central aperture and being connected directly to said amplifier and said microphone, the other portion of said cable being wound upon said other spool and serving as a connection between said amplifier and a utilization point.

8. A microphone arrangement comprising a casing having an aperture suilicient'to permit the insertion of said microphone, ai cable and spool located within said casing, said spool having a hollow portion adjacent the winding space for said cable, and an amplifier disposed within said lhollow portion which is electrically connected to said microphone by said cable.

ERWIN GERLACH. 

